Semiconductor processing methods are methods utilized in the fabrication of various structures associated with semiconductor substrates. For instance, semiconductor processing methods are utilized for the fabrication of integrated circuitry across semiconductor wafers.
Semiconductor processing often involves fabrication of multiple levels of integrated circuitry, with the various levels being stacked one over the other. Electrical contacts are formed to extend between the levels, and to thus interconnect the various levels with one another. Difficulties may occur in aligning the contacts to an underlying level.
One method that has been developed to address such difficulties is the utilization of so-called self-aligned contacts. A self-aligned contact may be formed by providing sacrificial material over a region where an electrical contact is ultimately to be made, and providing patterned material around the sacrificial material. Subsequently, the sacrificial material may be removed selectively relative to the patterned material to leave an opening aligned with the location where electrical contact is to be made.
It is common to utilize silicon dioxide as a sacrificial material, and to use silicon nitride for the patterned material to which the silicon dioxide is selectively removed. Part of the reason why such processing is common is that numerous etches are known which remove silicon dioxide with high selectively relative to silicon nitride. Unfortunately, such etches often utilize very high bias, and can damage silicon nitride structures. The etches can be particularly detrimental to corners of silicon nitride structures, and will generally round such corners. In some instances, the etches may even remove enough corner material to create facets at locations that had initially been corners. Overly aggressive etching may remove enough silicon nitride to expose underlying conductive materials, which can then lead to undesired electrical shorting between adjacent electrical components.
A continuing goal of semiconductor processing is to increase integration; and accordingly to decrease the size of individual components, and to decrease the spacings between individual components. Conventional methods of etching silicon dioxide sacrificial materials relative to silicon nitride are becoming increasingly difficult to scale to the smaller dimensions associated with increased integration.
It is desired to develop new semiconductor processing methods which reduce or avoid the above-discussed problems.